1. Field of the Invention
The present invention relates to an optical deflector.
2. Description of the Related Art
A two-dimensional optical deflector, which two-dimensionally deflects light beams, includes two galvano deflectors, which are orthogonally arranged and each of which respectively have a mirror. When such a two-dimensional optical deflector actually deflects a light beam, the locus of the light beam distorts on an image plane.
U.S. Pat. No. 4,838,632 discloses a two-dimensional optical deflector that reduces such distortion. FIGS. 29 and 30 show the two-dimensional optical deflector disclosed in U.S. Pat. No. 4,838,632. FIG. 29 is a view of the two-dimensional optical deflector viewed along a line XXIX—XXIX in FIG. 30. FIG. 30 is a view of the two-dimensional optical deflector viewed along a line XXX—XXX in FIG. 29.
As shown in FIGS. 29 and 30, a two-dimensional optical deflector 500 includes a first deflector 510 and second deflector 520. The first deflector 510 includes a movable portion 512 having a reflecting surface and a bracket 514 supporting the movable portion 512 to allow it to rock about a first axis A1. The second deflector 520 causes the first deflector 510 to rock about a second axis A2 perpendicular to the first axis A1. The first deflector 510 is fixed to the second deflector 520 so that the reflecting surface of the movable portion 512 forms an angle of 45° with respect to the second axis A2 in the non-deflection mode.
An incident light beam LB1 to be deflected falls on the first deflector 510 so as to be parallel to the second axis A2. A light beam LB2 reflected by the reflecting surface of the movable portion 512 falls on an image plane 534 through a lens 532.
The two-dimensional optical deflector 500 realizes a reduction in the distortion of the locus of a light beam on an image plane in spite of the fact that the deflector has a simple arrangement and is very compact.
In the two-dimensional optical deflector 500, the second deflector 520 causes the first deflector 510 integrally to rock about a rocking axis parallel to the incident light beam. For this reason, the size, mass, and moment of inertia of the first deflector 510 are important factors in realizing a compact two-dimensional optical deflector with a simple arrangement.
The specification of U.S. Pat. No. 4,838,632, however, provides no teaching or suggestion about the specific arrangement of the first deflector. In addition, the specification also provides no teaching or suggestion about a method of fixing the first deflector 510 to the second deflector 520 so that the reflecting surface of the movable portion 512 in the non-deflection state forms an angle of 45° with respect to the second axis A2.